1. Field of the Invention
The invention relates to an apparatus for recording and reproducing information with a ring buffer for recording and reproducing image signals by using its area circularly.
2. Description of Related Art
In recent years, hard disk recorders are attracting a great attention as a recording device in which a program provided by television broadcast or the like is recorded onto a hard disk instead of a video tape. When a hard disk is used as a recording medium, the following function, for example, can be realized. That is, while the program which is broadcasted is being recorded, the recorded program can be simultaneously reproduced (hereinafter, referred to as a time shift reproduction). A ring buffer area is provided in the hard disk in order to realize the time shift reproduction.
FIG. 1 is a diagram for explaining the recording and reproducing operations in the ring buffer area when performing the time shift reproduction.
In FIG. 1, a write position WP indicates a present recording position in the ring buffer area and a read position RP indicates a present reproducing position in the ring buffer area. These positions WP and RP gradually move independently from a head position to a last position of the ring buffer area, as shown by blank arrows in FIG. 1, respectively. When each of the positions WP and RP reaches the last position, the position returns to the head position and again gradually moves toward the last position. The speed at which each of the positions WP and RP moves depends on the bit rate of a video signal of a broadcast program selected as a recording or reproduction target. In this case, the broadcast program selected as a reproduction target is not limited to the television broadcast but can be a radio broadcast program having audio sounds only.
In the ring buffer area, the continuous recording and reproducing operations in a range from the head to the last of the area are executed respectively and independently. Furthermore, these operations are executed circularly in the area. By the operations described above, the time shift reproduction is executed in which the recorded broadcast program is reproduced from the position shown by RP while the broadcast program provided by the TV broadcast is being recorded to the position in the ring buffer area denoted as WP.
In the digital broadcast channel, broadcast programs of different bit rates such as HDTV (High Definition Television) broadcast programs of high picture quality and SDTV (Standard Definition Television) broadcast programs of a standard picture quality exist mixedly. Therefore, while the HDTV broadcast program of the high bit rate is being recorded, if the SDTV broadcast program of the low bit rate is reproduced in a state where the write position WP and the read position RP are close to each other as shown in FIG. 1, a state where the WP outruns the RP occurs. If the write position WP outruns the read position RP, then contents of the SDTV broadcast program which have not been reproduced yet will be halfway overwritten by the contents of the HDTV broadcast program.
In the time shift reproduction, however, the user cannot previously know the occurrence of the outrunning state as mentioned above.